<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    var str = '我是“JavaScript”，JavaScript是一门弱类型语言'
    console.log(str);
    console.log(str.indexOf('Java'));
    console.log(str.slice(15,25));
    console.log(str.slice(28));
    console.log(str.replace('JavaScript','张三'));
    // console.log(str.toUpperCase('JavaScript'))
    var newStr = str.slice(0,str.lastIndexOf('JavaScript'))+str.slice(str.lastIndexOf('JavaScript')).toUpperCase();
    console.log(newStr);
</script>
</html>